Diffusion control layers in diffusion transfer photographic products

ABSTRACT

Polymers comprising recurring units having cyclic β-elimination moieties capable of undergoing β-elimination in an alkaline environment and are disclosed for use in diffusion control layers in diffusion transfer photographic products.

BACKGROUND OF THE INVENTION

The present invention relates to photography and particularly toproducts adapted for employment in forming photographic diffusiontransfer images. In particular, the present invention is directed towardthe use of certain polymers in diffusion control layers of photographicdiffusion transfer film units.

SUMMARY OF THE INVENTION

According to the present invention, there are disclosed certain polymerscomprising recurring units having cyclic β-elimination moieties whichundergo β-elimination in an alkaline environment. The polymers can beused to convert a layer comprising one or more of the polymers from acondition of impermeability to alkali or materials soluble in orsolubilized by an aqueous alkaline processing composition to a conditionof substantial permeability thereto. Polymeric layers having theseβ-eliminating polymers can be used as diffusion control interlayers orovercoats in photosensitive elements or negative components of diffusiontransfer film units or as timing layers or overcoats in image-receivingelements or positive components of diffusion transfer film units.

Polymers useful according to the present invention for the provision ofdiffusion control layers in photographic products comprise certainessential recurring units having a cyclic β-elimination moiety capableof undergoing β-elimination in an alkaline environment. These polymerscomprise recurring units of the formula ##STR1## wherein

R is hydrogen, halogen (e.g., chloro) or lower alkyl (e.g., methyl);

L is an organic divalent linking group ##STR2## and

Z is a cyclic β-elimination moiety capable under alkaline conditions ofundergoing a β-elimination reaction and having the formula ##STR3##wherein

Y is ##STR4##

A represents the atoms necessary with Y to complete a four- toseven-membered ring structure, and D and E are independently hydrogen,methyl or phenyl, provided that not more than one of D and E is methylor phenyl, or said cyclic β-elimination moiety is a moiety having theformula ##STR5## wherein A and E together represent the atoms necessaryto complete with the carbon atoms to which they are bonded a five-, six-or seven-membered ring structure, D represents hydrogen, methyl orphenyl and Y is an activating group for said β-elimination reaction.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings.

THE DRAWINGS

FIG. 1 is a cross-sectional view of a photographic film unit includingdiffusion control layers of this invention;

FIG. 2 is a cross-sectional view of an image-receiving element includinga diffusion control timing layer of this invention;

FIG. 3 illustrates a model arrangement for measuring the "hold-time" ofinterlayers of this invention; and

FIG. 4 is a graphical depiction of dye density as a function of time ina system including an interlayer of the present invention.

DETAILED DESCRIPTION

As mentioned hereinabove, the polymers herein described are capable ofconverting a layer comprising one or more of said polymers from acondition of impermeability to alkali or materials soluble in orsolubilized by an aqueous alkaline processing composition to a conditionof substantial permeability thereto by undergoing a β-eliminationreaction in an alkaline environment. Polymeric layers comprising thesepolymers can be used as diffusion control layers in diffusion transferfilm units. These diffusion control layers can be used as overcoats orinterlayers in photosensitive elements and negative components ofdiffusion transfer film units or as timing layers or overcoats inimage-receiving elements and positive components of diffusion transferfilm units. The diffusion control layers hereof function by forming animpermeable "barrier" layer which prevents passage or diffusiontherethrough of either alkali or materials soluble in or solubilized byan aqueous alkaline processing composition for a predetermined length oftime during processing of the film unit and then converting over arelatively short time period to a condition of substantial permeabilityto these materials as a result of the polymers hereof undergoingβ-elimination. These diffusion control layers are thus "hold-release"layers in that materials intended to be subject to diffusion control bythe layer are "held" in place for a predetermined period of time andthen are "released" in substantial quantity over a relatively short timeperiod, i.e., allowed to rapidly diffuse through the layer. Thisdesirable "hold-release" behavior may be contrasted with the diffusioncontrol properties of those diffusion control layers which are notcapable of undergoing a precipitous change in permeability but ratherare initially permeable to some degree, and thus allow a slow leakage ofmaterial from the start of processing, and gradually become morepermeable during the processing interval.

The polymers useful in the diffusion control layers hereof compriseessential recurring units capable of undergoing β-elimination and havingthe formula (I) ##STR6## wherein R is hydrogen, halogen (e.g., chloro)or lower alkyl (e.g., methyl). In these recurring units, L is an organicdivalent linking group, described in more detail hereinafter, and Zrepresents a cyclic β-elimination moiety which is capable of undergoinga β-elimination reaction under alkaline conditions and which, therefore,contains the atoms requisite for the conduct of such β-eliminationreaction. The β-elimination Z moiety contains a cyclic structure andconforms to the formula (IIA or IIB): ##STR7##

From inspection of the β-elimination moities of formulas (II A) and (IIB), it will be seen that a proton is bonded in each instance to a carbonatom to which is also bonded an activating group, Y. This activatinggroup activates abstraction of the labile proton atom under alkalineconditions, thus, effecting the conduct of a β-elimination mechanism.

In the β-elimination moiety of formula (II A), i.e., the moiety of theformula ##STR8## Y represents either of the divalent radicals ##STR9##and is a part of a ring structure. A represents the atoms necessary withY and the respective carbon atoms to which they are bonded to complete afour-to seven-membered ring structure. D and E independently representhydrogen, methyl or phenyl, provided that not more than one of D and Eis methyl or phenyl. Preferably, both D and E will be hydrogen. In thecyclic moiety of formula (II A), A can represent, for example, adivalent radical such as methylene, dimethylene, trimethylene ortetramethylene to complete, with the Y radical and the carbon atoms towhich A and Y are bonded, a four-, five-, six- or seven-membered ringstructure, respectively. Suitable β-elimination moieties of formula (IIA) are the following moieties shown in formulas (III A) through (III D):##STR10## wherein, in each instance, Y is ##STR11## and A and D have themeanings aforedescribed. Preferably, in these β-elimination moieties,each of D and E will be hydrogen.

In general, a β-elimination reaction involves the elimination or removalof two groups from a parent molecule, these groups being substituted onadjacent atoms, i.e., beta to each other. The β-elimination reaction orremoval results in the formation of a more unsaturated bond, usually adouble bond, between the adjacent atoms. Referring to a polymercomprising the recurring units of formula (I) wherein the linking groupL is ##STR12## and the cyclic β-elimination moiety Z is a moiety of theformula (III B), the β-elimination reaction and mechanism can berepresented as follows: ##STR13## wherein B⁻ is an anionic base. Theabove reaction scheme shows the formation of an anionic polymer speciesas the result of the β-elimination. The anionic polymer unit iseffectively a leaving group removed from the parent molecule (startingpolymer) in order to effect formation of the double bond of theunsaturated cyclic compound, i.e., ##STR14##

Inspection of the β-elimination moiety of formula (II B), i.e., themoiety of the formula ##STR15## will show that the β-eliminationactivating group can be present in the cyclic β-elimination moietieshereof as a ring substituent. In these β-elimination moieties, A and Etogether represent the atoms necessary to complete with the carbon atomsto which they are bonded a five-, six- or seven-membered ring structure.D represents hydrogen, methyl or phenyl and, preferably, is hydrogen. Aand E together can represent, for example, trimethylene, tetramethyleneor pentamethylene to provide a five-, six- or seven-membered ringstructure, respectively. Suitable examples of β-elimination moities offormula (II B) are the following moieties shown in formulas (IV A)through (IV D): ##STR16## wherein, in each instance, Y represents aβ-elimination activating group.

In the β-elimination moieties of formula (II B), and those of formulas(IV A) through (IV D), Y represents any activating group which isphotographically innocuous and which is capable of stabilizing thecarbanionic species formed by abstraction of the acid-labile proton byan anionic base. A study of such activating groups has been provided byJ. Crosby and C. J. M. Stirling in J. Chem. Soc., B, p. 671. Activatinggroups which can be used in the present invention include sulfones ofthe formula --SO₂ W wherein W is aryl, aralkyl, alkaryl, alkyl, amino,or substituted amino; carbonyl groups of the formula ##STR17## wherein Tis hydrogen, alkyl, alkoxy, amino, or substituted amino; sulfoxidegroups of the formula ##STR18## wherein G is aryl, alkyl, alkaryl oraralkyl; nitro; and cyano. Preferred groups which activate theβ-elimination reaction are activating groups Y of the formula --SO₂ Wwherein W is alkyl (e.g., methyl or ethyl) or alkaryl (e.g., p-tolyl).

In the polymers comprising the recurring units of formula (I), i.e.,recurring units of the formula ##STR19## L represents an organicdivalent linking group. The nature of this linking group can vary andcan, for example, be the group ##STR20## characteristic of polymersderived from acrylic, methacrylic or 2-chloroacrylic acid. It will beappreciated that the nature of the linking group and its molecularconfiguration and size can influence the properties of the resultingpolymer and the rate of the desired β-elimination and that choice of asuitable linking group may in part be influenced by syntheticconsiderations and ready availability of reactants for the production ofthe polymers hereof. The linking group ##STR21## is a preferred linkinggroup and can be introduced into the desired polymer from readilyavailable acrylic materials.

The linking group can also be a group having the formula IV ##STR22##wherein R¹ is hydrogen or lower alkyl; R² and R³ can each independentlybe hydrogen; lower alkyl, e.g., methyl, ethyl, propyl, isopropyl;substituted lower alkyl, e.g., hydroxymethyl, hydroxyethyl,methylthioethyl; aryl, e.g., phenyl, naphthyl; alkaryl, e.g., tolyl;aralkyl, e.g., benzyl; cycloalkyl, e.g., cyclohexyl; or R² and R³together with the carbon atom to which they are bonded can constitute acarbocyclic or heterocyclic ring, e.g. ##STR23## or R³, when substitutedon the methylene carbon atom next adjacent the nitrogen atom shown informula (V) can be taken together with R¹ to form part of a substitutedor unsubstituted N-containing ring, e.g., ##STR24## and n is a positiveinteger one to six. It will be appreciated that each of the n number of##STR25## groups can be substituted the same or differently.

It will be appreciated that polymers having the recurring units offormula (I) wherein the linking group corresponds to that of formula (V)will comprise recurring units of the following formula (VI): ##STR26##wherein R, R¹, R² and R³ and Z have the meanings hereinbefore described.

Other suitable linking groups include those having the formula (VII):##STR27## wherein R⁴ is alkylene (e.g., ethylene). These linking groupswhich contain a carbamate moiety and can be derived from anisocyanatoalkyl ester, provide suitable linking to a β-eliminationmoiety. Polymers comprising the recurring units of formula (I) whereinthis carbamate containing linking group is present will have the formula(VIII): ##STR28## wherein R, R⁴ and the cyclic β-elimination moiety Zhave the meanings previously ascribed. Monomers and polymers having theabove-described carbamate-containing linkage, i.e., polymers containingthe recurring units of formula (VIII), and photographic productsincluding such polymers are disclosed and claimed in the patentapplication of Lloyd D. Taylor, U.S. Ser. No. 454,448, filed of evendate.

Other linking groups L can be suitably employed in the polymers hereofhaving the recurring units of formula (I) provided that the linkinggroup does not adversely and unacceptably influence the desiredβ-elimination reaction required for the preparation of polymericdiffusion control layers as described herein and is photographicallyinnocuous.

Examples of polymers that can be employed for the preparation ofpolymeric diffusion control layers in photographic products includepolymers containing recurring units of the following formulas: ##STR29##

The polymers employed herein can be homopolymers or copolymers,including graft or block copolymers. The copolymers can contain unitsprovided by copolymerization with various ethylenically unsaturatedmonomers such as alkyl acrylates, alkyl methacrylates, acrylamides, andmethacrylamides. In general, these comonomeric units are utilized toprovide particular predetermined properties to the polymer such ascoatability and viscosity and, in particular, predetermined permeabilitycharacteristics.

In general, the polymers employed herein will contain the recurringβ-elimination units in an amount sufficient to provide to a diffusioncontrol layer the capacity for appreciable conversion from a relativelyimpermeable condition to a condition of relative permeability uponβ-elimination and, thus, to provide functionality to the diffusioncontrol layer as set forth herein. In the copolymers the proportion ofthe β-elimination units to the total units of the polymer will varydepending on the nature of the particular β-elimination units employed,the nature of comonomeric and polymeric materials utilized therewith,and upon the particular and predetermined permeability characteristicsdesired.

According to a preferred embodiment of the present invention, thepolymers employed herein will comprise β-elimination units of formula(I) wherein R is hydrogen or methyl, the divalent linking group L is##STR30## or a linking group having the formula (V) or (VII), and cyclicβ-elimination moiety Z is a β-elimination moiety having the structure offormula (III B). These β-elimination units have the formula (IX).##STR31## wherein, preferably, D and E are each hydrogen and Y is --SO₂.

As mentioned previously, the polymers of this invention can becopolymers comprising the β-elimination monomeric units and a variety ofcomonomeric units incorporated into the polymer to impart theretopredetermined properties. For example, the "hold time", i.e., the timeinterval during which a diffusion control layer remains impermeableduring processing, can be affected by the relative hydrophilicity of thelayer resulting from incorporation of a given comonomer or mixture ofcomonomers into the β-elimination polymer. In general, the morehydrophobic the polymer, the slower will be the rate of permeation ofalkali into a diffusion control layer to initiate the β-eliminationreaction, i.e., the longer the hold time. Alternatively, adjustment ofthe hydrophobic/hydrophilic balance of the polymer by inclusion ofappropriate comonomeric units may be used to impart selectivepermeability characteristics to a diffusion control layer as appropriatefor a given usage within a film unit. For example, as detailedhereinbelow, it is highly preferred that diffusion control interlayersin the negative component of the film unit be initially substantiallypermeable to alkali, water, and various other components of theprocessing composition while substantially impermeable to theimage-providing materials of the film unit up to a predetermined pointin the development process. Such selective permeability may be achievedin the present invention by inclusion of appropriate comonomeric units,generally of a relatively hydrophilic nature, into the β-eliminationpolymers hereof or, more particularly, by "balancing" the hydrophobicand hydrophilic moieties to achieve the desired permeability.

Examples of suitable comonomers for use in the present invention includeacrylic acid; methacrylic acid; 2-acrylamido-2-methylpropane sulfonicacid; N-methyl acrylamide; methacrylamide; ethyl acrylate; butylacrylate; methyl methacrylate; N-methyl methacrylamide; N-ethylacrylamide; N-methylolacrylamide; N,N-dimethyl acrylamide; N,N-dimethylmethacrylamide; N-(n-propyl)acrylamide; N-isopropyl acrylamide;N-(β-hydroxy ethyl) acrylamide, N-(β-dimethylamino)acrylamide;N-(t-butyl) acrylamide; N-[β-(dimethylamino)ethyl]methacrylamide;2-[2'-(acrylamido)ethoxy]ethanol; N-(3'-methoxy propyl)acrylamide;2-acrylamido-3-methyl butyramide; acrylamido acetamide; methacrylamidoacetamide; 2-[2'-methacrylamido-3'-methyl butyramido]acetamide; anddiacetone acrylamide.

As examples of useful copolymers of this invention mention may be madeof the polymers of:

(1) 3-sulfolanyl methacrylate/styrene (70/30 parts by weight): ##STR32##(2) 3-sulfolanyl methacrylate/diacetone acrylamide/styrene (56/30/14parts by weight)

(3) 3-sulfolanyl-N-acrylyl-2-methylalanine/methylmethacrylate (56/44parts by weight)

(4) N-(methacryloxyethyl)-3-sulfolanyl carbamate/styrene (70/30 parts byweight) ##STR33## The β-elimination reaction which the β-eliminationpolymers of the diffusion control layers of this invention undergoensures that those materials intended to be subject to diffusion controlby the diffusion control layer are "held" in place for a predeterminedperiod of time and then "released" over a relatively short time period,the polymer layer undergoing a relatively rapid increase inhydrophilicity and water swellability and, thus, permeability as aresult of the β-elimination reaction. The predetermined hold time may beadjusted as appropriate for a given photographic process by means suchas controlling the mole ratio or proportion of β-elimination units inthe polymer; altering the thickness of the diffusion control layer;incorporating appropriate comonomeric units into the β-elimination toimpart thereto a desired hydrophobic/hydrophilic balance or degree ofcoalescence; utilizing different activating groups Y to affect the rateof β-elimination; or utilizing other materials, particularly polymericmaterials, in the diffusion control layer to modulate the permeationtherethrough of alkali or aqueous alkaline processing composition,thereby altering the time necessary for substantial β-elimination tooccur. This latter means of adjusting the hold time of the layer mayinclude, for example, utilization of a matrix polymer material having apredetermined permeability to alkali or aqueous alkaline processingcomposition as determined, for example, by the hydrophobic/hydrophilicbalance or degree of coalescence thereof. In general, increasedpermeability to alkali or aqueous alkaline processing composition and,thus, a shorter hold time, may be obtained by increasing thehydrophilicity of the matrix polymer or decreasing the degree ofcoalescence.

In addition to affecting the hold time of the diffusion control layersof this invention, matrix polymers may also be used to modulate thepermeability of the layers to alkali or materials soluble or insolubilized by an aqueous alkaline processing composition and thusaffect the functionality of the layers within a film unit. For example,relatively hydrophobic matrix polymers or matrix polymers having arelatively high degree of coalescence may help to render diffusioncontrol layers hereof substantially impermeable to alkali untilβ-elimination occurs, thus providing functionality to such layers asalkali neutralization timing layers or overcoat layers inimage-receiving elements and positive components of diffusion transferfilm units. Alternatively, relatively hydrophilic matrix polymers ormatrix polymers having a relatively low degree of coalescence may helpto render diffusion control layers hereof initially permeable to alkaliwhile remaining impermeable to materials soluble in or solubilized by anaqueous alkaline processing composition, e.g., image dye-providingmaterials, until β-elimination occurs, thus providing functionality tosuch layers as interlayers or overcoat layers in photosensitive elementsand negative components of diffusion transfer film units.

Utilization of matrix polymers can thus provide an alternative orcomplementary means to the above-mentioned use of suitable comonomers inthe β-elimination copolymers hereof as a method of modulating the holdtime or functionality of the diffusion control layers of this invention.It will be understood, however, that the β-elimination reaction isnecessary to achieve the relatively rapid change in permeability of thelayer.

Matrix/β-elimination polymer systems adapted to utilization in adiffusion control layer may be prepared by physical mixing of therespective polymers, or by preparation of the matrix polymer in thepresence of the β-elimination polymer. As disclosed in U.S. Pat. No.4,297,431 of Charles Sullivan, issued Oct. 17, 1981, a preferredmatrix/β-elimination polymer system comprises the system whereby aβ-elimination polymer is formed in the presence of a preformed matrixpolymer. Polymers which may be used as matrix polymers will generally becopolymers which comprise comonomeric units such as acrylic acid;methacrylic acid; methylmethacrylate; 2-acrylamido-2-methylpropanesulfonic acid; acrylamide; methacrylamide; N,N-dimethylacrylamide;ethylacrylate; butylacrylate; diacetone acrylamide; acrylamidoacetamide; and methacrylamido acetamide. The comonomeric units, as wellas the ratios thereof, should be chosen on the basis of the physicalcharacteristics desired in the matrix polymer and in the diffusioncontrol layer in which it is to be utilized. For example, a morehydrophilic and thus a generally more permeable matrix material can behad by increasing the respective ratio of hydrophilic comonomers, suchas acrylic acid or methacrylic acid, within the matrix polymer.

Matrix polymer/β-elimination polymer systems useful in the presentinvention include those listed below wherein 3-SMA designates3-sulfolanyl methacrylate MESC designatesN-(methacryloxyethyl)-3-sulfolanyl carbamate, DAA designates diacetoneacrylamide, BA designates butyl acrylate, AA designates acrylic acid, MAdesignates methacrylic acid, MMA designates methyl methacrylate and AMPSdesignates 2-acrylamido-2-methylpropane sulfonic acid. In the matrixsystems listed below the specified β-elimination polymer was polymerizedin the presence of the specified preformed matrix polymer. All ratiosand proportions are in parts by weight:

    ______________________________________                                        Matrix                                                                        System  Components                                                            ______________________________________                                        A       70 parts of a 48.9/42.6/8/0.5 matrix                                          copolymer of DAA/BA/AA/AMPS and 30 parts                                      of 80/20 poly(MESC-co-MMA)                                            B       70 parts of a 50.5/44/5/0.5 matrix                                            copolymer of DAA/BA/AA/AMPS and 30 parts                                      of 70/30 poly(3-SMA-co-DAA)                                           C       70 parts of a 48.9/42.6/8/0.5 matrix                                          copolymer of DAA/BA/AA/AMPS and 30 parts                                      of 68.5/29.5/2 poly(3-SMA-co-DAA-co-AA)                               D       70 parts of a 48.9/42.6/8/0.5 matrix                                          copolymer of DAA/BA/AA/AMPS and 30 parts                                      of 80/20 poly(3-SMA-co-MA)                                            ______________________________________                                    

The polymers hereof can be utilized in a number of diffusion transferproducts and processes based upon imagewise transfer of a diffusibleimage-providing material, e.g., a diffusible dye, dye intermediate, orsoluble silver complex. The diffusion transfer film units of the presentinvention comprise as essential layers, a support layer; at least onephotosensitive silver halide emulsion layer having associated therewitha diffusion transfer process image-providing material; an alkalineprocessing composition permeable image-receiving layer; and at least onediffusion control layer comprising the polymers of this invention.Following photoexposure, the silver halide emulsion is developed with anaqueous alkaline processing composition and, as a function ofdevelopment, an imagewise distribution of diffusible image-providingmaterial is formed which is transferred, at least in part, to thesuperposed image-receiving layer. The diffusion control layers of suchfilm units may be used to control diffusion of alkali or of theimage-providing material in accordance with the disclosures containedherein.

Film units within the present invention include those wherein the silverhalide emulsion layers and the image-receiving layer are initiallycontained in separate elements. Such film units may thus comprise: (a) aphotosensitive element comprising a support layer which is preferablyopaque and a negative component comprising at least one photosensitivesilver halide emulsion layer having associated therewith a diffusiontransfer process image-providing material; (b) an image-receivingelement comprising a support layer which may be opaque or transparent asappropriate for a given process and a positive component comprising animage-receiving layer; and (c) a diffusion control layer comprising thepolymers of this invention in at least one of said photosensitiveelement or image-receiving element. The respective elements may bebrought into superposition subsequent or prior to exposure. Subsequentto exposure, an aqueous alkaline processing composition is distributedbetween the superposed elements to initiate development. If theimage-receiving element provides an opaque reflective background, theimage formed may be viewed as a reflection print upon separation of theelements. By using a transparent image-receiving element, the resultantimage may be viewed as a transparency upon separation of the elements.Alternatively, if the photosensitive element and/or processingcomposition contains a light reflecting layer, e.g., a white pigmentsuch as titanium dioxide, the image may be viewed as a reflection printagainst the background provided by the light-reflecting layer, withoutseparation of the elements. The photosensitive element may also comprisea neutralization layer, e.g., an acid polymer layer, and a timing layerpositioned between the support layer and the negative component with theneutralization layer positioned adjacent the support. By conduct of aneutralization reaction between the acid-reactive sites of theneutralization layer and the alkali provided by the processingcomosition the environmental pH of the film unit may be lowered, thusproviding benefits detailed hereinbelow. The timing layer functions toprevent premature pH reduction by slowing diffusion of the alkali towardthe neutralization layer.

The diffusion control layers of this invention can also be used indiffusion transfer film units wherein the photosensitive layers andimage-receiving layer are in a single element, i.e. integralnegative-positive film units wherein the negative and positivecomponents are contained in a photosensitive laminate or otherwiseretained together in a superposed relationship at least prior toexposure. For example, the diffusion control layers herein can be usedin integral film units of the type described in detail in U.S. Pat. No.3,415,644, which film units are particularly adapted for formation ofcolor images. Film units of this type include, for example, thosecomprising: (a) a photosensitive laminate comprising a compositestructure containing, in sequence, an opaque support layer, preferablyan actinic radiation-opaque flexible sheet material, a negativecomponent comprising at least one photosensitive silver halide emulsionlayer having associated therewith an image dye-providing material, apositive component comprising an image-receiving layer dyeable by theimage dye-providing material, and a transparent support layer,preferably an actinic radiation transmissive flexible sheet material,the photosensitive laminate also comprising a diffusion control layercomprising the polymers of the present invention; (b) means retaining anaqueous alkaline processing composition integrated with the film unit sothat the processing composition can be distributed betwen the negativeand positive components. In this type of film unit a light-reflectingpigment is preferably provided by the processing composition such thatthe distribution of the processing composition between the negative andpositive components provides a light-reflecting layer against which adye image formed in the image-receiving layer can be viewed withoutseparation of the components.

The diffusion control layers of this invention can also be used inintegral negative-positive film units of the type described in U.S. Pat.No. 3,594,165. Film units of this type include, for example, thosecomprising: (a) a photosensitive laminate comprising, in sequence, atransparent support layer, preferably an actinic radiation transmissiveflexible sheet material, a positive component comprising animage-receiving layer, a processing composition permeable,ligh-reflecting layer against which a dye image formed in theimage-receiving layer can be viewed, and a negative component comprisingat least one photosensitive silver halide emulsion layer havingassociated therewith an image dye-providing material; (b) a transparentsheet superposed substantially coextensive the surface of thephotosensitive laminate opposite the transparent layer; (c) meansretaining an aqueous alkaline processing composition, which includes anopacifying agent, integrated with the film unit such that the processingcomposition can be distributed between the photosensitive laminate andthe transparent sheet; and (d) a diffusion control layer comprising apolymer of the present invention, which layer may be a component of thephotosensitive laminate or a coating on that side of the transparentsheet contiguous the photosensitive laminate. Color images formed withinthe image-receiving layer can be viewed against the background of thelight-reflecting layer without separation of the transparent sheet fromthe photosensitive laminate.

Multicolor images may be prepared in the film units of the presentinvention which comprise at least two selectively sensitized silverhalide emulsion layers, each associated with an image dye-providingmaterial which provides an image dye possessing spectral absorptioncharacteristics substantially complementary to the predominantsensitivity range of its associated emulsion. The most commonly employednegative components for forming multicolor images are of the tripackstructure and contain blue, green, and red sensitive silver halidelayers each having associated therewith in the same or a contiguouslayer a yellow, a magenta, and a cyan image dye-providing materialrespectively. It is preferred that each of the silver halide emulsionlayers, and its associated image dye-providing material, be spaced fromthe remaining emulsion layers, and their associated image dye-providingmaterials, by separate alkaline solution permeable interlayers, such asthose provided by the instant invention.

As disclosed in U.S. Pat. No. 2,983,606 and a number of other patents,image dye-providing materials which are particularly useful in formingcolor images by diffusion transfer are the dye developers, i.e.,compounds which contain, in the same molecule, both the chromophoricsystem of a dye and also a silver halide developing function. In atypical diffusion transfer system, each dye developer is associated witha separate silver halide emulsion layer and is, most preferably,substantially soluble in the reduced form only at the first pH providedby the processing composition, possessing subsequent to photoexposure orprocessing a spectral absorption range substantially complementary tothe predominant sensitivity range of its associated emulsion. Followingphotoexposure, the processing composition is applied and permeates theemulsion layers to initiate development of the latent image containedtherein. The dye developer is immobilized or precipitated in exposedareas as a consequence of the development of the latent image. Inunexposed and partially exposed areas of the emulsion, the dye developeris unreacted and diffusible and thus provides an imagewise distributionof unoxidized dye developer dissolved in the liquid processingcomposition, as a function of the point-to-point degree of exposure ofthe silver halide emulsion. At least part of this imagewise distributionof unoxidized dye developer is transferred, by imbibition, to asuperposed image-receiving layer, said transfer substantially excludingoxidized dye developer. The image-receiving layer receives a depthwisediffusion, from the developed emulsion, of unoxidized dye developerwithout appreciably disturbing the imagewise distribution thereof toprovide the reversed or positive color image of the developed image. Theimage-receiving layer may contain agents adapted to mordant or otherwisefix the diffused, unoxidized dye developer. Subsequent to substantialtransfer image formation, it is preferred that the environmental pH ofthe film unit be adjusted downward to a second pH at which the residualdye developers remaining within the negative structure are precipitatedor otherwise rendered non-diffusible in either their reduced or oxidizedstate. The pH adjustment is generally accomplished by means of an acidneutralization layer, preferably a polymeric acid layer, as detailedhereinbelow.

For purposes of illustration, the present invention will hereinafter bedescribed in terms of dye developers which function as described above,although no limitation of the invention to the illustrative imagedye-providing materials is intended.

As illustrated in the accompanying drawings, FIG. 1 sets forth aperspective view of an integral film unit of the type described inreferenced U.S. Pat. No. 3,415,644, shown with the processingcomposition 26 distributed between the negative and positive components.Film unit 10 comprises photosensitive laminate 11 including in order,opaque support layer 12; cyan dye developer layer 13; red-sensitivesilver halide emulsion layer 14; interlayer 15; magenta dye developerlayer 16; green-sensitive silver halide emulsion layer 17; interlayer18; yellow dye developer layer 19; blue-sensitive silver halide emulsionlayer 20; overcoat layer 21; image-receiving layer 22; spacer layer 23;neutralizing layer 24; and transparent support layer 25. Followingphotoexposure through transparent support layer 25, processingcomposition 26, initially retained in a rupturable container (not shown)is distributed between overcoat layer 21 and image-receiving layer 22 toinitiate development of the silver halide emulsion layers. It ispreferred that processing composition 26 contains an opacifying agent ofthe type described for example, in U.S. Pat. No. 3,647,437, such thatthe layer of processing composition 26 is able to prevent furtherexposure of the photosensitive layers of the film unit during theprocessing of the film unit outside of the camera. As a consequence ofdevelopment, an imagewise distribution of diffusible dye developer isformed which is transferred, at least, in part to image-receiving layer22. The layer provided by processing composition 26 preferably comprisesa light-reflecting pigment, such as titanium dioxide, against which thecolor image formed in image-receiving layer 22 can be viewed. Subsequentto substantial transfer image formation, a sufficient portion of thealkali provided by processing composition 26 permeates image-receivinglayer 22 and spacer layer 23, to gain access to neutralizing layer 24whereupon neutralization of the alkali occurs to lower the pH of thesystem to a level at which the dye developers are insoluble andnon-diffusible, to provide thereby a stable color transfer image.

Rather than being positioned between image-receiving layer 22 andsupport layer 25, spacer layer 23 and neutralizing layer 24 may bedisposed intermediate support layer 12 and cyan dye developer layer 13,with neutralizing layer 24 positioned adjacent to support layer 12. Inthis embodiment, the alkali provided by processing composition 26permeates layers 13 through 21 and spacer layer 23 to gain access toneutralizing layer 24 whereupon neutralization of the alkali is effectedas described hereinabove.

With multicolor diffusion transfer products such as those describedabove, undesirable inter-image effects may occur whereby a given dyedeveloper or other image dye-providing material is controlled as aresult of association with a silver halide emulsion layer other than theone with which it was initially associated in the film unit. Thisunintended associative relationship generally results from migration ofthe image dye-providing material to a silver halide layer other than theone with which it is initially associated prior to development of this"wrong" emulsion layer. As a result of this premature migration, theimage dye-providing material may acquire diffusion characteristicsopposite to those it would normally possess had it remained inassociation with its intended controlling silver halide layer. Forexample, if a dye developer prematurely migrates to a silver halidelayer other than the one with which it is initially associated, it mayundergo oxidation to a non-diffusible species as a function of thedevelopment of this "wrong" layer and will be rendered incapable oftransferring as intended to the image-receiving layer. As a result,accuracy in color reproduction and color saturation within the transferimage will be adversely affected. In addition, a portion of a second dyedeveloper which should have undergone oxidation as a function of thedevelopment of this "wrong layer" remains in a reduced and diffusiblestate and, thus, may transfer to contaminate the resultant colortransfer image. These inter-image effects may be more specificallyexemplified by reference to FIG. 1. If it is possible for the magentadye-developer of layer 16 to back-diffuse to red sensitive silver halideemulsion layer 14 before substantial development of this layer andresultant substantial formation of an imagewise distribution of the cyandye developer in layer 13, some of the magenta dye developer may becomeoxidized and rendered non-diffusible as a function of red exposure anddevelopment of the red sensitive emulsion layer. Thus, there is produceda loss in magenta dye density in the transfer image. Moreover, thatportion of cyan dye developer which should have been oxidized inpreference to the magenta dye developer remains in the reduced form andmay diffuse to image-receiving layer 22 with resultant cyan dyecontamination of the transfer image. Thus, accurate color reproductionof a photographed object is hindered by such inter-image effects.

To obviate or minimize inter-image effects, diffusion control layershereof may be employed as interlayers positioned between the respectivesilver halide layers, and their associated dye developers, such asinterlayers 15 and 18 in FIG. 1. The β-elimination step undergone by theβ-elimination polymer(s) within these layers ensures a delay inpermeability of these layers during initial processing of the film unitand thus "holds" the dye developer and substantially prevents diffusionto unassociated silver halide layers at least until after substantialdevelopment of these layers and formation of the intended imagewisedistributions of the dye developers. The "release" of the diffusible dyedevelopers should occur prior to substantial fogging of the emulsionlayer with the most rapid fogging rate. It will be appreciated that the"hold-release" behavior of the interlayers of this invention providesadvantages over those interlayers which allow a slow leaking of dyedeveloper at the start of the processing interval in that the dyedevelopers are better confined to their associated emulsion layer duringthe critical initial development interval and then released rapidly andin substantial quantity so as to allow rapid and essentiallysimultaneous transfer of the color image-forming materials.

In addition to minimizing the above described inter-image effects,interlayers comprising the polymers of this invention may be used toprovide increased capacity for accurate color reproduction over a rangeof temperatures. In general, the lowering of the temperature at whichprocessing occurs slows both the rate of development and the rate of dyediffusion. If the respective rates are slowed disproportionately, i.e.,if the decrease in the development rate is proportionately greater thanthe decrease in the rate of diffusion, color reproduction may beadversely affected by diffusion of the dye away from its associatedemulsion layer prior to substantial development of that layer. This typeof premature migration may be minimized by use of interlayers comprisingthe polymers of this invention which have been found to provide markedlylonger "hold" times at lower temperatures, e.g., 7° C. relative to the"hold" time observed at higher temperatures, e.g., 24° C. Thus, theinterlayers may be utilized to hold the dye developer in associationwith the silver halide emulsion for longer time periods at lowertemperatures to accommodate the system to slower development rates atthese temperatures while allowing for a proportionately faster "release"as the temperature and development rate increase.

The polymers of this invention useful as interlayer materials asdescribed hereinabove can also be utilized in overcoat layers ofphotosensitive elements or negative component overcoat layers such asovercoat layer 21 in FIG. 1. Such overcoat layers can be used, forexample, to prevent premature migration of the dye developer mostproximate to the distributed processing composition or to provide ameans by which the various color image-forming materials may be madeavailable essentially simultaneously to the mordant sites within theimage-receiving layer.

The processing compositions employed in diffusion transfer processes ofthe type contemplated herein usually are highly alkaline, having a pH inexcess of 12 and frequently in excess of 14 or higher. In general, thehighly alkaline environment facilitates the conduct of dye diffusion toprovide satisfactory diffusion rates and image dye densities. Asdisclosed in U.S. Pat. No. 3,362,819 it is highly desirable that theenvironmental pH of the film unit be lowered to at least 11 or lowersubsequent to substantial transfer image formation to achieve improvedstability of the dye image. U.S. Pat. No. 3,415,644 discloses that inintegral film units wherein the negative and positive components remainin a superposed contiguous relationship subsequent to substantialtransfer image formation, an in-process adjustment of the environmentalpH of the film unit from a pH at which transfer processing is operativeto a pH at which dye transfer is inoperative subsequent to substantialtransfer image formation is highly desirable in order to achieve a morestable dye transfer image in terms of the chemical and light stabilityof the image dye molecules and in terms of preventing post-processingtransfer of residual image dye-providing materials within the negativestructure to the image-receiving layer.

As disclosed in previously referenced U.S. Pat. No. 3,362,819, reductionin the environmental pH of the film unit is preferably achieved byconduct of a neutralization reaction between the alkali provided by theprocessing composition and a layer comprising immobilized acid reactivesites, i.e., a neutralization layer. Preferred neutralization layers arethose comprising a polymeric acid such as cellulose acetate hydrogenphthalate; polyvinyl hydrogen phthalate; polyacrylic acid; polystyrenesulfonic acid; and partial esters of polyethylene/maleic anhydridecopolymers.

Premature pH reduction, as evidenced, for example, by a decrease inimage dye density, can be prevented by disposing intermediate theneutralization layer and the distributed processing composition a spaceror timing layer which slows diffusion of the alkali toward theneutralization layer. As indicated hereinabove, diffusion control layersof this invention may be used as such timing layers, forming an alkaliimpermeable barrier for a predetermined time interval and thenconverting to a relatively alkali permeable condition upon occurrence ofβ-elimination to allow the alkali access to the neutralization layer ina rapid and quantitavely substantial fashion.

The timing layers comprising the β-elimination polymers hereof can beused in image-receiving elements of the type disclosed in U.S. Pat. No.3,362,819 or as a component part of the positive component of integralnegative-positive film units of the type disclosed in previouslyreferenced U.S. Pat. Nos. 3,415,644 and 3,594,165. Alternatively, thetiming and neutralization layers may be associated with the negativecomponent as is disclosed, for example, in U.S. Pat. Nos. 3,362,821 and3,573,043. In film units of the present invention of the type disclosedin referenced U.S. Pat. No. 3,594,165, these layers may also be carriedby the transparent sheet employed to facilitate application of theprocessing composition.

Illustrated in FIG. 2 is an image-receiving element of the presentinvention. Image-receiving element 27 comprises, in order, a supportlayer 28, a neutralizing layer 29, a spacer or timing layer 30comprising a β-elimination polymer of the present invention, and animage-receiving layer 31. During processing the image-receiving layer issituated contiguous the layer of processing composition. The processingcomposition penetrates image-receiving layer 31 to provide a sufficientpH for image formation therein and is then subsequently neutralized bypenetrating through timing layer 30 upon β-elimination of the diffusioncontrol polymer contained therein to gain access to neutralizing layer29.

As indicated previously, the permeability of the diffusion controllayers of this invention to alkali may be controlled in a predeterminedmanner by the use of comonomeric units which provide to the polymer asuitable hydrophilic/hydrophobic balance and/or a suitable degree ofcoalescence or by the use of a matrix material providing the requiredhydrophilicity or coalescence. In general, increased hydrophobicity andcoalescence will render the diffusion control layer relatively lesspermeable to alkali and to the processing composition prior to theβ-elimination reaction.

In a further embodiment of the present invention, an overcoat layercomprising the polymers hereof may be provided to the image-receivingelement or positive component of the film unit contiguous theimage-receiving layer and opposite the neutralization layer. Overcoatlayers of this type in this position within the film unit may functionto control diffusion of alkali or materials soluble in or solubilized byan aqueous alkaline processing composition.

The permeation characteristics of the polymers hereof utilized in timinglayers can be evaluated by measuring the time necessary for downwardadjustment of the environmental pH to a predetermined lower level asevidenced by color transition of an indicator dye, preferably initiallycontained in the processing composition, from a colored form at theinitially high processing composition pH to a colorless form at saidpredetermined lower pH level. Evaluations of this type may be carriedout utilizing a test structure comprising in order a support, apolymeric acid layer, a test timing layer, and an image-receiving layer.A transparent cover sheet is superposed coextensive the test structurecontiguous to the image-receiving layer and an alkaline processingcomposition comprising an indicator dye which is highly colored at a pHof 12 or higher and colorless below a predetermined lower pH level ofabout 9 or 10 is spread between the cover sheet and the image-receivinglayer. The indicator dye remains colored, and may be viewed as suchthrough the transparent cover sheet, until the alkali penetrates throughthe test timing layer to gain access to the polymeric acid whereuponneutralization of a substantial portion of the alkali present occurs tolower the pH to a level at which the indicator dye is colorless. Themeasurement of the time necessary for substantial "clearing" of theindicator is generally referred to as the "clearing time". Teststructures comprising timing layers which allow a slow initial leakageof alkali and gradually become more permeable show no precipitous changein color but rather a gradual clearing while structures comprising thetiming layers described herein will show a precipitous change in colorafter an initial delay evidencing the rapid change in alkalipermeability undergone by the timing layer upon β-elimination.

The capacity of diffusion control layers comprising polymers hereof todelay permeation therethrough of dye image-providing materials untilconversion by β-elimination to a relatively dye-permeable condition canbe evaluated by utilization of the test structure shown in FIG. 3. Inaccordance with such structure, transfer of the image dye-providingmaterial through the test diffusion control layer is monitored inrelation to time. The "hold-release" properties of the β-eliminationpolymer test material can be evaluated in simulation of the functioningof the material, e.g., an interlayer in a photosensitive element. Suchtest structure and a suitable method of evaluation are set forth indetail in Example 4.

The polymers hereof containing the recurring units of formula (I) can bereadily prepared by polymerization in known manner of a correspondingpolymerizable monomeric compound of the formula (X): ##STR34## whereineach of R, L and Z have the meanings as aforedescribed. Thepolymerizable monomer (X) can be prepared by resort to a variety ofsynthetic procedures depending, for example, upon the nature of thelinking group L. For example, when the linking group L is a carboxylateradical, i.e., ##STR35## the polymerizable monomer can be suitablyprepared by reaction of an unsaturated acid, or anhydride or halidethereof, with an alcohol of the formula Z--OH wherein Z is a cyclicβ-elimination moiety as defined previously. Thus, Z can be aβ-elimination moiety of the formula (II A) or (II B), such as themoieties of formulas (III A) through (III D) and (IV A) through (IV D),and the cyclic alcohol can be reacted with the unsaturated acid,anhydride or halide.

The production of 3-sulfolanyl methacrylate can be illustrated by thereaction of a mixture of methacrylic acid and trifluoroacetic anhydridewith 3-hydroxysulfolane in a trifluoroacetic acid reaction solvent. Thecompounds 3-sulfolanyl acrylate and 3-sulfolanyl methacrylate andsuitable methods for their production are described, for example, inU.S. Pat. No. 3,257,319 (issued June 21, 1966 to R. H. Raines et al.)and by A. H. Ahlbrecht et al., J. Am. Chem. Soc. 75, 984(1952).

Suitable cyclic alcohol compounds Z--OH for production of monomericcompounds of formula (X) where L is the carboxylate linking groupinclude, for example, such alcohols as 3-hydroxy-thietane dioxide;3-hydroxy-sulfolane, 3-hydroxythiane dioxide; 3-hydroxy-cyclopentanone;3-hydroxy-cyclohexanone; 1-cyano-2-hydroxy-cyclopentane;1-hydroxy-2-methylsulfonyl cyclopentane; 1-hydroxy-2-(p-tolyfulfonyl)cyclohexane; and 3-hydroxy-4-(methylsulfonyl)-tetrahydrofuran.

Polymerizable monomers of formula (X) wherein linking group L is alinking group corresponding to formula (V) herein can be prepared, forexample, by the reaction of an acrylyl or methacrylyl chloride,anhydride or ester of the formulae ##STR36## respectively, wherein R isas previously defined and R⁵ is alkyl or aryl, with a primary orsecondary amine of the formula ##STR37## wherein R¹, R², R³, Z and n areas previously defined. The resulting monomeric compound bypolymerization provides a polymer comprising recurring units having theformula (VI) hereinbefore.

A preferred method for production of polymerizable monomers of formula(X) where L is linking group of the type represented by formula (V)involves the reaction of a 2-alkenyl-5-oxazalone of the formula##STR38## (wherein R, R² and R³ have the meanings previously provided)with a cyclic alcohol of the formula Z--OH wherein Z is a β-eliminationmoiety as previously defined, i.e., a β-elimination moiety of formula(II A) or (II B). This reaction is illustrated by the following reactionscheme; ##STR39##

The preparation of polymerizable monomers of formula (X) wherein linkinggroup L corresponds to formula (V) can be suitably effected by employingthe synthetic procedures described in U.S. Pat. No. 4,288,523 (issuedSept. 8, 1981 to L. D. Taylor) except that an alcohol of the formulaZ--OH as herein defined is utilized in place of the alcohol compoundsthere utilized. The disclosure of U.S. Pat. No. 4,288,523 isincorporated herein by reference.

Polymerizable compounds of formula (X) wherein linking group L is acarbamate-containing linkage of formula (VII) can be suitably preparedby the reaction of a polymerizable isocyanato ester of acrylic,methacrylic or 2-chloroacrylic acid having the formula (VI): ##STR40##(wherein R and R¹ are as previously defined) with an alcohol of theformula Z--OH wherein Z has the aforedescribed meaning. Any of the Z--OHalcohols previously described can be utilized for this purpose. Thereaction is illustrated by reference to the following reaction schemewhich shows the reaction of β-cyanatoethyl methacrylate and 3-hydroxysulfolane to form N-(methacryloxyethyl)-3-sulfolanyl carbamate:##STR41##

The polymerizable isocyanato esters (XI) utilized as starting materialsfor the production of the polymerizable monomeric carbamate compounds ofthe invention include the isocyanatoalkyl esters of such ethylenicallyunsaturated acids as acrylic acid, methacrylic acid and 2-chloroacrylicacid. Suitable isocyanoalkyl esters are the β-isocyanatoethyl esterssuch as the β-isocyanatoethyl esters of these ethylenically unsaturatedacids. A preferred starting material is β-isocyanatoethyl methacrylatewhich can be effectively utilized for the production of monomericcarbamate compounds of the invention. The isocyanatoalkyl ester startingmaterials (IV) are known compounds and their method of preparation isdescribed, for example, in U.S. Pat. No. 2,718,516 (issued Sept. 20,1955 to N. M. Bortnick).

The monomeric compounds of formula (X) can be prepared in any of avariety of inert solvents. It will be appreciated, for example, thatisocyanate groups exhibit reactivity toward compounds having a labileproton and, accordingly, hydroxyl-containing or amine-containing solventmaterials will be desirably avoided where compounds having acarbamate-containing linkage are desirably employed. Suitable solventsinclude tetrahydrofuran, chloroform, dichloromethane, dimethylformamide,benzene, dioxane, toluene, acetone, methylethylketone, and ethylacetate. The reactions, in general, may be conducted over temperatureranges of about 0° C. to about 100° C. and preferably about 15° C. toabout 40° C. but will vary with the particular compound prepared. Ingeneral, the reactions can be facilitated by use of a tin catalyst suchas stannous octanoate, a tertiary amine catalyst such as triethylamine,a 4-dialkylaminopyridine catalyst, e.g., 4-(N,N-dimethylamino)pyridineor 4-pyrrolidinopyridine. If desired, a small amount of polymerizationinhibitor such as hydroquinone or t-butylpyrocatechol also be presentduring the reactions.

The monomers prepared by any of the above methods may be polymerizedaccording to different polymerization techniques such as bulk, solution,suspension, or emulsion polymerization. In addition, the polymerizationmay be conducted in the presence of other suitable polymers, i.e., apolymeric matrix material, to prepare a matrix system which may be usedas a diffusion control layer. The polymerization can be initiatedchemically, e.g., by suitable free radical or redox initiators or byother means such as heat or incident radiation. As examples of chemicalinitiators, mention may be made of azobisisobutyronitrile, potassiumpersulfate, sodium bisulfite, benzoyl peroxide, diacetyl peroxide,hydrogen peroxide, and diazoaminobenzene. It will be appreciated thatthe chosen means of initiation should be substantially incapable ofdegrading or otherwise adversely reacting with either the reactants orproducts of the reaction. The amount of catalyst used and the reactiontemperature may be varied to suit particular needs. Generally, thepolymerization should proceed satisfactorily by carrying out thereaction at a temperature between 25° C. and 100° C. and using less than5% by weight of initiator, based on the starting weight of thepolymerizable monomer or monomers.

The polymers of the present invention, i.e., the polymers of formula (I)can be prepared by resort to an alternative procedures. Thus, ifdesired, the monomeric precursor compound can first be polymerized andthe resulting polymer can be derivatized by reaction with an alcohol ofthe formula Z--OH wherein Z has the aforedescribed meaning. This isillustrated by the following reaction scheme: ##STR42##

The present invention is further illustrated in the following Exampleswhich are illustrative only and not intended to be of limiting effect.Unless otherwise stated, all parts of percentages are by weight.

EXAMPLE 1

Preparation of N-(methacryloxyethyl)-3-sulfolanyl carbamate ##STR43##

3-hydroxysulfolane (81.70 grams; 0.60 mole) was dissolved in methylenechloride (250 mls.) in a 500-ml., round bottom flash equipped withmagnetic stirrer, thermometer and water condenser topped with a dryingtube. Anhydrous magnesium sulfate (5.0 grams) and 3-Angstrom, powderedzeolitic molecular sieve material (10.0 grams) were added and thecontents were stirred for one hour at room temperature. To the flask wasadded β-isocyanatoethyl methacrylate (77.58 grams; 0.50 mole) and 6.11grams (0.05 mole) of 4-(N,N-dimethylamino)pyridine were added in oneportion. The resulting exotherm caused boiling of the methylene chlorideand an ice bath was utilized to prevent refluxing. The reaction vesselwas cooled for about 1.5 hours and was then stirred at room temperatureovernight. Total reaction time was about 22.5 hours. The reactioncontents were filtered, then stirred with 200 mls. of ice water and fourmls. of glacial acetic acid for one-half hour. The aqueous phase wasseparated and the organic phase was washed sequentially with water(1×200 mls.), brine (1×200 mls.), 1% sodium bicarbonate solution (1×200mls.), brine (1×200 mls.) and was dried with magnesium sulfate. Theproduct was decolorized with charcoal, filtered and 15 mgs. of4-methyl-2,6-ditertbutyl phenol were added. A viscous yellow liquid wasrecovered after evaporation of solvent in vacuo. The product, whichslowly crystallized on standing, was dissolved in a minimum of ethylacetate (about 600 mls. product provided about 800 mls. of solution).Hexane (600 mls.) was added to the cloud point and the solution wascooled to -20° C. An additional 100-150 ml. quantity of hexane was addedand the solution was again cooled. A white, solid product was recoveredby filtration and was washed with hexane, air and, then, vacuum dried toyield 120.74 grams (82.9% yield) of product having a melting point of70.5°-71.5° C. Molecular structure was confirmed by nuclear magneticresonance and thin layer chromatographic techniques.

    ______________________________________                                                      % C  % H     % N    % S   % O                                   ______________________________________                                        Calculated for C.sub.11 H.sub.17 NO.sub.6 S                                                   45.35  5.88    4.81 11.01 32.95                               Found           45.54  6.01    4.71 10.97 --                                  ______________________________________                                    

EXAMPLE 2

Preparation of a matrix system comprising a matrix terpolymer consistingof 48.9 parts by weight of diacetone acrylamide, 42.6 parts by weight ofbutyl acrylate, 8.0 parts by weight of acrylic acid, and 0.5 parts byweight of 2-acrylamido-2-methylpropane sulfonic acid and a β-eliminationcopolymer consisting of 68.5 parts by weight of 3-sulfolanylmethacrylate, 29.5 parts by weight of diacetone acrylamide and 2 partsby weight of acrylic acid wherein the ratio by weight of matrix polymerto β-elimination polymer is 70:30.

A mixture of 0.0405 grams of ferrous sulfate heptahydrate, 26.36 gramsof a 23.9% by weight dialyzed Dowfax solution (Dowfax 2Al solutionavailable from the Dow Chemical Company, Midland, Mich.), 16.8 grams ofa 100% solution of Triton X-100 (available from Rohm and Haas Corp.Philadelphia, Pa.) and 3.6 liters of water was heated to 65° C. under anitrogen atmosphere and to this mixture were added simultaneously, inseparate streams, over a period of two hours:

(a) a mixture of 1026.8 grams of diacetone acrylamide, 168 grams ofacrylic acid, 10.5 grams of 2-acrylamido-2-methylpropane sulfonic acid,35.15 grams of a 23.9% by weight dialized Dowfax solution; and 2.1liters of water;

(b) 894.7 grams of butylacrylate;

(c) a solution of 7.64 grams of potassium persulfate in 200 millilitersof water; and

(d) a solution of 2.89 grams of sodium bisulfite in 100 milliliters ofwater.

Following completion of the additions, 254.9 grams of the resultingmatrix polymer were treated in the following manner. Five grams of waterand one gram of dialyzed Dowfax solution were added to the polymericmatrix. The matrix was purged with nitrogen and the temperature wasraised to 55° C. Over a period of about 20 minutes, 47.8 grams of 1%sodium hydroxide solution were added in a dropwise manner. The resultingneutralized matrix polymer was held under a nitrogen atmosphere for 30minutes.

To the neutralized polymeric matrix material prepared as aforedescribedwere added simultaneously, in separate streams, over about 45 minutes:

(e) a mixture of 19.11 grams of 3-sulfolanyl methacrylate, 8.22 gramsdiacetone acrylamide and 0.56 gram of acrylic acid;

(f) a solution of 0.2027 gram of potassium persulfate and 20 millilitersof water; and

(g) a solution of 0.1201 gram of sodium bisulfite in 20 milliliters ofwater.

Following completion of these additions, the temperature of the mixturewas maintained at 55° C. for three hours. Yield of 376.9 grams of amatrix system having a solids concentration of 25% by weight.

EXAMPLE 3

Preparation of a matrix system comprising a matrix terpolymer consistingof 48.9 parts by weight of diacetone acrylamide, 42.6 parts by weight ofbutyl acrylate, 8.0 parts by weight of acrylic acid, and 0.5 parts byweight of 2-acrylamido-2-methylpropane sulfonic acid and β-eliminationcopolymer consisting of 80 parts by weight ofN-(methacryloxyethyl)-3-sulfolanyl carbamate and 20 parts by weight ofmethyl methacrylate wherein the ratio by weight of matrix polymer toβ-elimination polymer is 70:30.

A polymeric matrix was prepared according to the procedure set forth inEXAMPLE 2 except as follows. Upon completion of the addition of streams(a) through (d), 274.5 grams of the resulting matrix polymer weretreated in the following manner. Five grams of water and 1.08 grams of18% dialyzed Dowfax solution were added to the polymer matrix. Thematrix was purged with nitrogen and the termperature was raised to 55°C. Over a period of about 20 minutes, 51.5 grams of 1% sodium hydroxidesolution were added in a dropwise manner. The resulting neutralizedmatrix polymer was held under a nitrogen atmosphere fro 30 minutes.

To the neutralized polymeric matrix material prepared as aforedescribedwere added simultaneously, in separate streams, over about 45 minutes:

(e) a mixture of 24.18 grams of N-(methacryloxyethyl)-3-sulfolanylcarbamate and 5.82 grams methyl methacrylate;

(f) a solution of 0.2183 gram of potassium persulfate and 20 millilitersof water; and

(g) a solution of 0.1293 gram of sodium bisulfite in 20 milliliters ofwater.

Following completion of these additions, the temperaline was maintainedat 55° C. for three hours. Yield of 402 grams of a matrix system havinga solids concentration of 25.3% by weight.

EXAMPLE 4

Beta-elimination polymers were evaluated using a test structure, 32 inFIG. 3, comprising a transparent support 33, a layer 34 comprising about215 mg./m² of a cyan dye developer of the formula ##STR44## about 430mg./m² gelatin, and about 16 mg./m.² of succindialdehyde and a layer 35containing about 2150 mg./m.² of the polymeric material. Layers 34 and35 were coated sequentially on support 33 using a conventional loopcoater.

A transparent sheet 37 comprising a polyester clear film base wassuperposed with test structure 32 and an opaque alkaline processingcomposition 36 comprising:

    ______________________________________                                        Potassium hydroxide (45% aqueous solution)                                                               23.94  g.                                          Benzotriazole              1.33   g.                                          6-Methyl uracil            0.73   g.                                          Bis-(β-aminoethyl)-sulfide                                                                          0.06   g.                                          Colloidal silica, aqueous dispersion                                                                     4.48   g.                                          (30% SiO.sub.2)                                                               Titanium dioxide           92.12  g.                                          N--phenethyl α-picolinium bromide                                                                  6.18   g.                                          (50% aqueous solution)                                                        N--2-hydroxyethyl-N,N'N'--triscarboxymethyl                                                              1.82   g.                                          ethylene diamine                                                              4-Amino pyrazolo(3,4d)pyrimidine                                                                         0.61   g                                           Carboxymethyl hydroxyethyl cellulose                                                                     4.82   g.                                          Water                      100    g.                                          ______________________________________                                    

was introduced between polymeric test material layer 35 and transparentsheet 37 at a gap of 0.071 mm. Immediately after introduction of theprocessing composition the optical reflection density to red light ofthe sample was monitored through transparent support 33 as a function oftime by use of a MacBeth Quanta-Log densitometer equipped with astrip-chart recorder. The density measured as a function of time wasthat of the cyan dye developer in the original dye-containing layer 34and the cyan dye developer in polymer test layer 35. Dye developer whichhad diffused through test layer 35 into the processing composition wasmasked by the titanium dioxide contained therein and, thus, did notcontribute to the red absorption. In this manner, the diffusion of dyedeveloper through the test layer and into the processing compositioncould be monitored.

In FIG. 4 is shown a curve of red absorption density as a function oftime where t₁ is the time for the cyan dye developer to become wetted bythe processing composition, t₂ is the total time the cyan dye developeris held back by the polymer interlayer, D_(o) is the absorption densityafter dissolution of the dye developer, and D_(f) is the finalabsorption density of the residual dye developer remaining in layers 34and 35 after completion of dye diffusion. The slope of the line segmentbetween A and B is calculated and serves as an indication of therapidity with which the test layer undergoes a change in dyepermeability.

The polymeric materials prepared as described in EXAMPLES 2 and 3 hereinwere coated and evaluated as test layer 35 in the above-described teststructure. In Table I, the values for t₁ and t₂ (in seconds) and slopeare reported.

                  TABLE 1                                                         ______________________________________                                        Polymeric Product                                                                              t.sub.1   t.sub.2                                                                             Slope                                        ______________________________________                                        Product of EXAMPLE 2                                                                           1         28    330                                          Product of EXAMPLE 3                                                                           0.5       61    135                                          ______________________________________                                    

What is claimed is:
 1. A photographic diffusion transfer film unit comprising:a support layer; a photosensitive silver halide emulsion layer having associated therewith a diffusion transfer process image-providing material; an alkaline processing composition permeable image-receiving layer; and at least one diffusion control layer comprising a polymer having recurring units of the formula ##STR45## wherein R is hydrogen, halogen or lower alkyl; L is an organic divalent linking group; and Z is a cyclic β-elimination moiety capable under alkaline conditions of undergoing a β-elimination reaction and having the formula ##STR46## wherein H is a labile proton abstractable under said alkaline conditions, Y is an activating group selected from ##STR47## said activating group being effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction, and A represents the atoms necessary with Y to complete a four- to seven membered ring structure, and D and E are independently hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl; or said cyclic β-elimination moiety Z is a moiety having the formula ##STR48## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, H is a labile proton abstractable under said alkaline conditions and Y is an activating group effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction.
 2. The diffusion transfer film unit of claim 1 wherein said cyclic β-elimination moiety has the formula ##STR49## wherein Y is ##STR50## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 3. The diffusion transfer film unit of claim 2 wherein Y is ##STR51## and each of D and E is hydrogen.
 4. The diffusion transfer film unit of claim 1 wherein said recurring units have the formula ##STR52## wherein R is hydrogen, halogen or lower alkyl, Y is ##STR53## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 5. The diffusion transfer film unit of claim 4 wherein R is methyl, Y is ##STR54## and each of D and E is hydrogen.
 6. The diffusion transfer film unit of claim 1 wherein said cyclic β-elimination moiety has the formula ##STR55## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, and Y is an activating group selected from the group consisting of sulfones of the formula --SO₂ W wherein W is aryl, aralkyl, alkaryl, alkyl, amino, or substituted amino; carbonyl groups of the formula ##STR56## wherein T is hydrogen, alkyl, alkoxy, amino, or substituted amino; sulfoxide groups of the formula ##STR57## wherein G is aryl, alkyl, alkaryl, or aralkyl; nitro and cyano.
 7. The diffusion transfer film unit of claim 6 wherein D is hydrogen, A and E together represent --CH₂ --CH₂ --CH₂ -- and Y is an activating group of the formula --SO₂ W where W is alkyl or alkaryl.
 8. The diffusion transfer film unit of claim 1 wherein said organic divalent linking group L has the formula ##STR58## wherein R¹ is hydrogen or lower alkyl; R² and R³ are independently hydrogen, lower alkyl, substituted lower alkyl, aryl, alkaryl, aralkyl, cycloalkyl, or R² and R³ together with the carbon atoms to which they are bonded constitute a carbocyclic or heterocyclic ring, or R³, when substituted on the methylene carbon atom next adjacent the nitrogen atom, is taken together with R¹ to form part of a substituted or unsubstituted N-containing ring; and n is a positive integer of one to six.
 9. The diffusion transfer film unit of claim 8 wherein R¹ is hydrogen, R² and R³ are each methyl and n is one.
 10. The diffusion transfer film unit of claim 9 wherein said β-elimination moiety Z is a moiety having the formula ##STR59##
 11. The diffusion transfer film unit of claim 1 wherein said diffusion control layer further comprises a matrix polymer.
 12. The diffusion transfer film unit of claim 11 wherein said matrix polymer is a copolymer comprising recurring comonomeric units selected from the group consisting of acrylic acid, methacrylic acid; methylmethacrylate; 2-acrylamido-2-methylpropane sulfonic acid; acrylamide; methacrylamide; N,N-dimethylacrylamide; ethylacrylate; butylacrylate; diacetone acrylamide; acrylamido acetamide; and methacrylamido acetamide.
 13. The diffusion transfer film unit of claim 1 wherein said image-providing material is a dye developer.
 14. The diffusion transfer film unit of claim 1 comprising at least two selectively sensitized silver halide emulsion layers, each associated with an image dye-providing material which provides an image dye possessing spectral absorption characteristics substantially complementary to the predominant sensitivity range of its associated emulsion, wherein said diffusion control layer is an interlayer positioned between said silver halide emulsion layers, and their associated image dye-providing materials.
 15. The diffusion transfer film unit of claim 1 wherein said diffusion control layer comprises an alkali neutralization timing layer.
 16. The diffusion transfer film unit of claim 1 wherein said diffusion control layer comprises a negative component overcoat layer.
 17. The diffusion transfer film unit of claim 1 wherein said diffusion control layer comprises a positive component overcoat layer.
 18. A photosensitive element for use in diffusion transfer photographic processes comprising:a support layer; a negative component comprising at least one photosensitive silver halide emulsion layer having associated therewith a diffusion transfer process image-providing material; and at least one diffusion control layer comprising a polymer having recurring units of the formula ##STR60## wherein R is hydrogen, halogen or lower alkyl; L is an organic divalent linking group; and Z is a cyclic β-elimination moiety capable under alkaline conditions of undergoing a β-elimination reaction and having the formula ##STR61## wherein H is a labile proton abstractable under said alkaline conditions, Y is an activating group selected from ##STR62## said activating group being effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction, and A represents the atoms necessary with Y to complete a four- to seven membered ring structure, and D and E are independently hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl; or said cyclic β-elimination moiety Z is a moiety having the formula ##STR63## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, H is a labile proton abstractable under said alkaline conditions and Y is an activating group effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction.
 19. The photosensitive element of claim 18 wherein said cyclic β-elimination moiety has the formula ##STR64## wherein Y is ##STR65## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 20. The photosensitive element of claim 19 wherein Y is ##STR66## and each of D and E is hydrogen.
 21. The photosensitive element of claim 18 wherein said recurring units have the formula ##STR67## wherein R is hydrogen, halogen or lower alkyl, Y is ##STR68## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 22. The photosensitive element of claim 21 wherein R is methyl, Y is ##STR69## and each of D and E is hydrogen.
 23. The photosensitive element of claim 18 wherein said cyclic β-elimination moiety has the formula ##STR70## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, and Y is an activating group selected from the group consisting of sulfones of the formula --SO₂ W wherein W is aryl, aralkyl, alkaryl, alkyl, amino, or substituted amino; carbonyl groups of the formula ##STR71## wherein T is hydrogen, alkyl, alkoxy, amino, or substituted amino; sulfoxide groups of the formula ##STR72## wherein G is aryl, alkyl, alkaryl, or aralkyl; nitro and cyano.
 24. The photosensitive element of claim 23 wherein D is hydrogen, A and E together represent --CH₂ --CH₂ --CH₂ -- and Y is an activating group of the formula --SO₂ W where W is alkyl or alkaryl.
 25. The photosensitive element of claim 18 wherein said organic divalent linking group L has the formula ##STR73## wherein R¹ is hydrogen or lower alkyl; R² and R³ are independently hydrogen, lower alkyl, substituted lower alkyl, aryl, alkaryl, aralkyl, cycloalkyl, or R² and R³ together with the carbon atoms to which they are bonded constitute a carbocyclic or heterocyclic ring, or R³, when substituted on the methylene carbon atom next adjacent the nitrogen atom, is taken together with R¹ to form part of a substituted or unsubstituted N-containing ring; and n is a positive integer one to six.
 26. The photosensitive element of claim 25 wherein R¹ is hydrogen, R² and R³ are each methyl and n is one.
 27. The photosensitive element of claim 26 wherein said β-elimination moiety Z is a moiety having the formula ##STR74##
 28. The photosensitive element of claim 18 wherein said diffusion control layer further comprises a matrix polymer.
 29. The photosensitive element of claim 28 wherein said matrix polymer is a copolymer comprising recurring comonomeric units selected from the group consisting of acrylic acid; methacrylic acid; methylmethacrylate; 2-acrylamido-2-methylpropane sulfonic acid; acrylamide; methacrylamide; N,N-dimethylacrylamide; ethylacrylate; butylacrylate; diacetone acrylamide; acrylamido acetamide; and methacrylamido acetamide.
 30. The photosensitive element of claim 18 wherein said image-providing material is a dye developer.
 31. The photosensitive element of claim 18 comprising at least two selectively sensitized silver halide emulsion layers, each associated with an image dye-providing material which provides an image dye possessing spectral absorption characteristics substantially complementary to the predominant sensitivity range of its associated emulsion, wherein said diffusion control layer is an interlayer positioned between said silver halide emulsion layers, and their associated image dye-providing materials.
 32. The photosensitive element of claim 31 further comprising a neutralization layer and a timing layer positioned between said support layer and said negative component, with the neutralization layer positioned adjacent said support layer.
 33. The photosensitive element of claim 18 wherein said diffusion control layer comprises an overcoat layer.
 34. An image-receiving element comprising:a support layer; a neutralizing layer; a diffusion control layer comprising a polymer having recurring units of the formula ##STR75## wherein R is hydrogen, halogen or lower alkyl; L is an organic divalent linking group; and Z is a cyclic β-elimination moiety capable under alkaline conditions of undergoing a β-elimination reaction and having the formula ##STR76## wherein H is a labile proton abstractable under said alkaline conditions, Y is an activating group selected from ##STR77## said activating group being effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction, and A represents the atoms necessary with Y to complete a four- to seven membered ring structure, and D and E are independently hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl; or said cyclic β-elimination moiety Z is a moiety having the formula ##STR78## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, H is a labile proton abstractable under said alkaline conditions and Y is an activating group effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction; and an image-receiving layer.
 35. The image-receiving element of claim 34 wherein said cyclic β-elimination moiety has the formula ##STR79## wherein Y is ##STR80## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 36. The image-receiving element of claim 34 wherein said recurring units have the formula ##STR81## wherein R is hydrogen, halogen or lower alkyl, Y is ##STR82## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 37. The image-receiving element of claim 36 wherein R is methyl, Y is ##STR83## and each of D and E is hydrogen.
 38. The image-receiving element of claim 34 wherein D is hydrogen, A and E together represent --CH₂ --CH₂ --CH₂ -- and Y is an activating group of the formula --SO₂ W where W is alkyl or alkaryl.
 39. The image-receiving element of claim 34 wherein said diffusion control layer comprises an alkali neutralization timing layer.
 40. The image-receiving element of claim 34 wherein said diffusion control layer comprises an overcoat layer.
 41. An integral negative-positive diffusion transfer film unit comprising:a photosensitive laminate comprising a composite structure containing, in sequence, an opaque support layer, a negative component comprising at least one photosensitive silver halide emulsion layer having associated therewith an image dye-providing material, a positive component comprising an image-receiving layer dyeable by the image dye-providing material, and a transparent support layer, the photosensitive laminate also comprising a diffusion control layer containing a polymer comprising recurring units of the formula ##STR84## wherein R is hydrogen, halogen or lower alkyl; L is an organic divalent linking group; and Z is a cyclic β-elimination moiety capable under alkaline conditions of undergoing a β-elimination reaction and having the formula ##STR85## wherein H is a labile proton abstractable under said alkaline conditions, Y is an activating group selected from ##STR86## said activating group being effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction, and A represents the atoms necessary with Y to complete a four- to seven-membered ring structure, and D and E are independently hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl; or said cyclic β-elimination moiety Z is a moiety having the formula ##STR87## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, H is a labile proton abstractable under said alkaline conditions and Y is an activating group effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction; and means retaining an aqueous alkaline processing composition integrated with the film unit so that the processing composition can be distributed between the negative and positive components.
 42. The diffusion transfer film unit of claim 41 wherein said processing composition comprises a light reflecting pigment such that distribution of the processing composition between the negative and positive components provides a light reflecting layer against which a dye image formed in said image-receiving layer can be viewed.
 43. The diffusion transfer film unit of claim 41 further comprising a neutralization layer and a timing layer positioned between said opaque support layer and said negative component, with the neutralization layer positioned adjacent said opaque support layer.
 44. The diffusion transfer film unit of claim 41 wherein said cyclic β-elimination moiety has the formula ##STR88## wherein Y is ##STR89## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 45. The diffusion transfer film unit of claim 44 wherein Y is ##STR90## and each of D and E is hydrogen.
 46. The diffusion transfer film unit of claim 41 wherein said recurring units have the formula ##STR91## wherein R is hydrogen, halogen or lower alkyl, Y is ##STR92## and D and E are each hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl.
 47. The diffusion transfer film unit of claim 46 wherein R is methyl, Y is ##STR93## and each of D and E is hydrogen.
 48. The diffusion transfer film unit of claim 41 wherein said organic divalent linking group L has the formula ##STR94## wherein R¹ is hydrogen or lower alkyl; R² and R³ are independently hydrogen, lower alkyl, substituted lower alkyl, aryl, alkaryl, aralkyl, cycloalkyl, or R² and R³ together with the carbon atom to which they are bonded constitute a carbocyclic or heterocyclic ring, or R³, when substituted on the methylene carbon atom next adjacent the nitrogen atom, is taken together with R¹ to form part of a substituted or unsubstituted N-containing ring; and n is a positive integer of one to six.
 49. The diffusion transfer film unit of claim 48 wherein R¹ is hydrogen, R² and R³ are each methyl and n is one.
 50. The diffusion transfer film unit of claim 49 wherein said β-elimination moiety Z is a moiety having the formula ##STR95##
 51. An integral negative-positive film unit comprising:a photosensitive laminate comprising, in sequence, a transparent support layer, a positive component comprising an image-receiving layer, a processing composition permeable, light-reflecting layer against which a dye image formed in said image-receiving layer can be viewed, and a negative component comprising at least one photosensitive silver halide emulsion layer having associated therewith an image dye-providing material; a transparent sheet superposed substantially coextensive with the photosensitive laminate opposite the transparent layer; means retaining an aqueous alkaline processing composition, which includes an opacifying agent, integrated with the film unit such that the processing composition can be distributed between the photosensitive laminate and the transparent sheet; and a diffusion control layer comprising a polymer comprising recurring units of the formula ##STR96## wherein R is hydrogen, halogen or lower alkyl; L is an organic divalent linking group; and Z is a cyclic β-elimination moiety capable under alkaline conditions of undergoing a β-elimination reaction and having the formula ##STR97## wherein H is a labile proton abstractable under said alkaline conditions, Y is an activating group selected from ##STR98## said activating group being effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction, and A represents the atoms necessary with Y to complete a four- to seven-membered ring structure, and D and E are independently hydrogen, methyl or phenyl, provided that not more than one of D and E is methyl or phenyl; of said cyclic β-elimination moiety Z is a moiety having the formula ##STR99## wherein A and E together represent the atoms necessary to complete with the carbon atoms to which they are bonded a five-, six- or seven-membered ring structure, D is hydrogen, methyl or phenyl, H is a labile proton abstractable under said alkaline conditions and Y is an activating group effective to activate abstraction of said labile proton under said alkaline conditions and to thereby activate said β-elimination reaction; said diffusion control layer being contained within said film unit as either a component of said photosensitive laminate or a coating on that side of said transparent sheet contiguous the photosensitive laminate.
 52. The diffusion transfer film unit of claim 51 wherein said recurring units have the formula ##STR100## wherein R is hydrogen, halogen or lower alkyl, Y is ##STR101## and D and E are each hydrogen methyl or phenyl, provided that not more than one of D and E is methyl or phenyl. 